It is known per se to configure an axial unit from a pin and at least one bearing sleeve for radially receiving the pin, the pin and the bearing sleeve forming slide bearing complementary elements which are assigned to one another. Here, the pin can absorb a force which acts perpendicularly with respect to the pin/bearing sleeve unit (slide bearing) and acts centrally or eccentrically on the pin.
A fastening unit comprising a pin/bearing sleeve unit of this type is customary, in particular, in commercially available belt tensioning systems. Belt tensioning systems are used, for example, in the timing drive or unit drive of vehicles having an internal combustion engine.
Belt tensioning systems having a tensioning roller which is arranged eccentrically in relation to the pin/bearing sleeve unit are known from the prior art, which tensioning roller is mounted rotatably via an eccentrically arranged roller bearing. It has been shown in the past that edge loading occurs between the pin and the bearing sleeve in a pin/bearing sleeve unit of belt tensioning systems having an eccentrically arranged tensioning roller. This edge loading causes an increased surface pressure on the pin and the bearing sleeve, with the consequence that the service life of said slide bearing can be reduced. In particular in the case of high eccentrically acting forces and a long service life, this leads to tilting, with the result that overall the guidance of the belt tensioning system is only insufficient for disruption-free operation.
Against this background, DE 195 33 457 A1 discloses a tensioning apparatus for a flexible drive having a piston which is loaded by a compression spring and is guided in a longitudinally displaceable manner for exerting a linear force on the flexible drive which is to be tensioned. In the disclosed tensioning apparatus, only centrally acting forces act on the bearing.
In contrast, DE 102 36 113 B3 has disclosed a rotary bearing having a slide bearing which has a stationary ceramic body having a bearing face. The ceramic material which is used has high wear resistance and can also provide a reliable and long-life rotary bearing in the case of high eccentrically acting forces and high temperatures (for example, as a result of friction).
It is disadvantageous here that the ceramic body can be introduced only with great expenditure into a slide bearing sleeve (bush) which is provided for receiving the ceramic body, as the material is difficult to introduce and requires a large amount of time on account of its dimensional stability. The ceramic body can be destroyed in the case of an increased pressing force on account of its brittle material property. The ceramic body can be introduced only by complicated and time-consuming heating of the slide bearing sleeve. This rotary bearing therefore proves to be complicated in assembly and expensive.
In addition, this document does not disclose a solution as to how wear phenomena which relate to the pin (the pin in a tensioning apparatus is not made from ceramic, but from hardened steel, for example) can be solved. Therefore, the service life of the known slide bearing is also comparatively low overall here. In addition, calibration or restriction of the tolerances likewise has negative effects on costs and service life.